1. Field of the Invention
This invention relates to a clamping cylinder system such as a diecast machine and an injection molding machine.
2. Description of the Related Art
Heretofore, there has been known a clamping cylinder system provided with a toggle type mold clamping mechanism in order to obtain a high clamping force by a small type cylinder in a diecast machine and the like.
In the conventional system, a change in pressure in the clamping cylinder system provided with this toggle type mold clamping system has been taught as in FIG. 3 for example. This drawing is recorded by an oscillograph, and, in which an oil pressure of the clamping cylinder is given as an ordinate and a clamping time is given on an abscissa. In this drawing, from a start time A of the clamping cylinder to a time B during which a movable mold is abutted against a stationary mold, it is relatively low because of frictional resistance of a movable portion. From the abutting point B of the movable mold against the stationary mold to a point C where a link of the toggle mechanism rises, the oil pressure can increase to obtain a predetermined clamping force. From the point C to D, the clamping cylinder is operated to clamp further. However, the scale-up magnification reaches the substantially maximum at the point C, the oil pressure is decreased accordingly. A point E indicates that a piston of the clamping cylinder reaches a point of stroke end where a supply pressure Ps is constant.
As apparent from the above, in the clamping system using the toggle type mold clamping mechanism, a cylinder output, i.e. a diameter, a pressure and the like are determined on the basis of the point C.
However, an inner diameter of the clamping cylinder determined on the basis of the point C would be relatively large to obtain a predetermined cylinder output, and moreover it would be necessary to increase a discharge value of an oil pump or compensate for the discharge value by an accumulator or the like. Accordingly, in this case, a pressure loss would be high, thus presenting a problem of high installation cost.
Further, when the inner diameter of the clamping cylinder is large, because a constant amount of oil is supplied, the moving speed of the piston is relatively reduced. As a result, the clamping time is necessarily long thus presenting the problem of a decrease in production.